Coil and method of making same



I June 26, 1928.

J. A. VICTOREEN COIL AND METHOD OF MAKING AME Filed April 28, 1924 2Sheets-Sheet INVENTOR 6 K 4475 7% BY @11 SW ATTORNEYS,

June 26, 1928. 1,674,934

J. A. VICTOREEN COIL AND METHOD OF MAKING SAME Filed April 1- -4 4" 'HM"28. 1924 2 Sheets-Sheet 2 W A u'm-u an .4- .m

INVENTOR awmvm an su lwm.

ATTORNEYkS.

Patented June 26, 19 28.

UNITED STATES JOHN AUSTIN VICTOREEN, OF CLEVELAND, OHIO.

COIL AND METHOD OF MAKING SAME.

Application filed April 28, 1924.

This invention relates to electrical coils and method of making thesame, and more particularly relates to an electrical coil, together withthe means and process for male ing the same, and which coil isparticularly adapted for use in electrical circuits where an extremelyhigh frequency current is employed, such as, for instance, in what arenown as radio circuits where the alternating current frequenciesemployed may be of the order of one million cycles per second.

It is a special object of my invention to provide a means and processfor making such coils in a single layer of wire, and which coil willsustain its form as wound without the addition of extraneous wiresupporting means such as a bobbin or the like.

It is a special object of my invention to provide such electrical coilsthat the wire thereon may be in a plurality of convolw tions, thesuccessive convolutions being suitably spaced, all of the successiveconvolutions being securely bound together flexibly by a binding layerof suitable composition, and which, preferably, does not enter thespaces between the successive turns to any considerable extent, but isdisposed tangentially' in contact with one side only of the turns ofwire, making this contact, preferably, on the external side of the coil.In this way the electrostatic capacity and dielectric losses had betweenthe turns is kept to a minimum, and at the same time, the binder firmlysecures the different turns together in a unitary form sustaining coilunit.

It is another object of my invention to provide a coil adaptable forradio circuit system purposes which may be wound in a certain form, orshape, such as that of a cylinzler, and which will be inherentlyform-sustaining, but which may be bent from such form as made by theapplication of sufficient force, and without breaking the successiveconvolutions of wire, which are held together by the binding material,andwhich when so bcnt will preferably retain a desired different form.

Another object of my invention is to provide suitable mechanism forgiving the coil its initial form. and which mechanism is removable fromthe coil at a later stage in the process.

Another object of my invention is to pro- Serial No. 709,630.

vide removable spacing means for the successive convolutions of wire inthe coil.

Another object of my invention is to provide a suitable insulatingbinder for the coil of my invention and which hinder will pos ess thenecessary properties of a suitable binder, which simplifies themanufacture of the coil, and to make the completed coil durable andchangeable as to form after being made and at the same time introduce aslittle as possible of electrostatic capacity and dielectric lossesbetween the successive convolutions of wire in the coil.

Another object of my invention is to provide an improved process formaking the improved coil herein described and which may be employed withsuitable obvious variations to coils of other forms than those hereinshown.

Another object of my invention is to economically produce coils of theabove general description and which may be made in relatively long axiallengths, and which may be very easily cut into shorter unitary formsustaining coils when such shorter coils with a fewer number of turns ofwire are desired, and the number of turns in such coils being accordingto the number desired.

Other objects of my invention and the invention itself will becomeapparent by reference to the following description and in whichdescription reference will be had to the accompanying drawings n which:

Fig. 1 shows a coil which is an embodi ment of my invention;

Fig. 2 shows a shorter coil which may be made from such a longer coil asshown in Fig. 1 by merely cutting the desired length of such shortercoil from the longer coil as along the dotted line of Fig. 1;

Fig. 3 shows a longitudinal medial section of the coil of Fig. 1;

Fig. 4 shows, in longitudinal medial section, the coil on a collapsiblewinding form or bobbin in an intermediate stage of manufacture,according to one method for making such coils. wherein spacing turns ofbare wire or other spacing material are disposed between adjacent turnsof the coil Winding, the intervening spacing turns being subsequentlyremoved after performing the initial spacing function;

Fig. 5 shows, in longitudinal medial section a coil such as that shownin Fig. 3,

after the winding binder has been applied, but subsequent to beingremoved from the collapsible winding form or bobbin and prior to theremoval of the spacing wire winding;

Fig. 6 shows a mandrel insertable longitudinally within such a coil asshown in Fig. 5 and upon which mandrel the extra intervening turns ofbare spacing wire or other material may be wound to remove such spacingturns in the production of the finished coil;

Fig. 7 shows a collapsible mandrel cylindrical in form, in plan, and u nwhich mandrel I may wind a coil wire, together with a spacing winding,for the production of such a finished coi as is shown in Fig. 5, andultimately as shown in Figs. 1 to 3 inclusive;

Fig. 8 shows another form of mandrel which I may em loy in making thecoil of Figs. 1 to 3, inc usive.

Referring now to the drawings in the different figures, by which I havedesignated like numbers by like reference characters, in Fig. 3 I showin longitudinal medial section a portion of a finished coil, the 0011also being shown in perspective in Fig. 1.

This coil, as shown, is cylindrical in form,-

comprising a plurality of turns of wire as at 2, and in theembodiment ofmy invention illustrated the successive turns are spaced from one end.At 3 I show an insulating binding material joining the successive turnsof wire in the coil, the bindin material 3 being approximately ofcylindrical form on its external side 4 and joining the successive turnsof wire by a cementing contact as at 5 on its inner surface. In the coilof my invention, I preferably-so dispose the cementing cylinder 4 thatthe successive turns 2 adhering thereto contact therewith only over aminimum area of the exterior surface of each such turn of wire andcementing function involving, where the winding is composed of insulatedwire, that portion of the insulation only which is contained on theouter surface of the turns. The nature of the contact between thebinding cylinder and the successive turns of wire which usually are ofcircular cross section, being in the nature of a tangent or pointcontact,

so far as such a contact can be approached in actual ractice.

The cy indrical winding, supporting tube 3, so formed and so carryingthe successive turns of wire, each properly spaced as may be desired, ispreferably composed of such a material as may be elastic to a degree andet sufficiently inelastic that if the tinished coil is bent withsufiicient abru tness that it may retain some part qf the isbortionoccasioned by such bending, so that by careful bending one may causesuch a coil winding to depart from the substantially cylindrical formherein illustrated and to take other forms, such as oval or moreirregular forms, such as that of a half circle, in transverse sectionalviews.

In this description, wherein the form of the coil is described as beingrimarily cylindrical, I wish it to be un erstood that my invention isnot limited to the making and to a coil of true cylindrical form, butthat it may be constructed to be primarily of various forms. such asconical or forms of differing width from the cylindrical and conicalforms, but only for e purpose of describing my invention in a referredembodimcnt do I refer to the cylindrical form of coil and show such inthe drawings accompanying this specification.

I find that for a suitable material with which to make the bindinginsulating layer 3, I can secure a very good result when this layer ismade of a congealed solution of commercial celluloid dissolved inacetone, the celluloid being dissolved in the acetone, the relativeproportions of celluloid and acetone bein preferably such that theresulting liquid prior to congealing is about the consistency ofcommercial maple syrup.

In constructing the coil of my invention, the turns of wire are arrangedin a suitable manner in the form which the finished coil is to takeprimarily and which may be so as to substantial] form a cylinder, asshown in Fig. 3, an the liquid binding material solution is applied overthe outside of the coil. precaution preferably being taken inapplication so that the film or layer of binding material does notpenetrate deeply between the spaces or interstices between thesuccessive turns of wire. \Vhere the film is applied to the coil as byspreading it thereon by a brush, I find that this can be bestaccomplished when the brush is operated in directions approximatelyparallel to the axis of the coil, that is, transversely to the directionof the turns comprising the winding. The coil is then cooled and thefilm or layer of binding material congealed from its liquid form intothat of a solid form, the congealing being accelerated suitably by theapplication of heat, but I find that with the binding materialcomposition heretofore mentioned, there is a practical limit to theamount of such acceleration by heating, in order that the finishedproduct be homogeneous and possess the proper mechanical and electricalqualities, and likewise that it may present a neat and pleasingappearance to the eye. If the process is hurried unduly, bubbling or theformation of air or gas bubbles detracts from the appearance andserviceability of the insulating binding film. A coil constructedaccording to this method will have its exterior surface composed entirely of the film insulating film and the exterior surface will. appearrelatively smooth,

whereas the interior of the coil being free from any contact with theexterior binding film will comprise merely the successive turns of wireseparated by air spaces, each turn of wire standin out sharply from theencircling insulating binding material. My invention comprehends themaking of coils wherein the inner surfaces of the successive turns areonly in contact with the binding insulating film, this being disposedinteriorly of the wire winding, but for all practical purposes I referthe form herein shown and described In order to make up the coil windinghav-.

ing the successive turns suitably spaced, where such spacing is desiredbetween successive turns I may accomplish this in a number of differentways, two of the ways being herein illustrated but others being wellknown in the art, some of these being for the purpose of my inventionmerely alternative and equivalent. A manner of accomplishing this, whichI prefer for some reasons, comprises the winding of a second wire notintended to be contained in the finished coil at the same time the coilwire is wound, the two wires being wound side by side on a suitablemandrel so that successive turns of wire on the mandrel as wound will,as shown in Fig. 4, comprise alternately a turn of electrical coil wire6 and a turn of spacing wire 7, the spacing wire 7 being preferablynon-insulated, and I find that a bare copper wire serves the purposebetter than an insulated wire for a reason which will become apparentlater. The true winding comprising turns 6 and the spacing windingcomprising turns 7 having been placed on the coil and the ends secured,as by inserting them through openings 22 in the mandrel, the windingbinding film of insulating material, as above described, is applied tothe exterior of the coil and the coil as wound is left on the mandreluntil the bindin film is sufliciently congealed that the coil Wlll beself form sustaining, the film turns being capable of hold ing the turnsin the form of the exterior wall of the mandrel. At such time the bolts14 are removed, the U-shaped mandrel expanding members 18 and 21 areremoved and the two sections of the mandrel are collapsed inwardly andthus disengaged from the inner surfaces of the winding convolutions, themandrel sections being thereupon removed by an axial movement from thein terior of the coil. The coil then is placed over a spacing wireremoving mandrel 23,

this mandrel comprising a bobbin having heads 24 of smaller externaldiameterthan the interior diameter of the coil into which the mandrel isto be inserted, and a handle 25 secured rigidly to one side of themandrel and by which handle the mandrel may be rotated. The m ndrel 23and the coil are then relatively rotated preferably by holding the coilstill and rotating the mandrel until the spacing turns of wire 7 are allremoved from the coil spaces between successive turns of coil wire 6, itbeing possible to so remove the spacing turns of wire since such wire isbare and contains no fibres to make a good cementing contact with thecongealed binder film, this binder film being that shown at 3 in Figs. 3and 5, and in certain other figures.

Fig. 5 shows the form of the coil before the removal of the spacingturns of bare wire, and Figs. 1 and 3 show the coil as it appears afterthe spacing turns have been removed. The finished coil, as shown inFigs. 1 and 3, may then be cut up into smaller coils of smaller axiallength, such as the coil of Fig. 2, which may be assumed to have beenseparated from the coil of Fig. 1 by cutting the binding film along thedotted line 26 and severing the turn of coil wire crossing such line. Inthis way economy may be accomplished in manufacture by making a singletubular coil of considerable length, the coil thereafter being divided.into smaller coils having the requisite number of turns of wire for thepurpose for which such coils may be intended.

While I have described a particular kind of mandrel as capable of beingused in connection with the production of the coil of my invention andin the process by which such a coil is produced, other forms of mandrelsmay be employed but not departing from my invention. For instance, I mayuse the mandrel as shown in Fig. 8, wherein the two sections as joinedtogether by bolts 37 and 38 and which bolts hold securely a mandrelsection spacing element 39 carrying at one or both of its outer ends,one'as shown, a handle 25, the outer surface of the mandrel containing aspiral groove 40, the successive groove convolutions being suitablyseparated, suitably formed ridges 41. Such a mandrel when used does notrequire the extra subsequently removed bare wire winding in order toprovide the proper spacing between the turns of wire of the finishedcoil, the ridges 41 providing the spacing and the coil winding bindingfilm maintaining this spacing after application. The ridges 41 alsoserve to prevent the insulating material from penetrating between theconvolutions of the coil, as the bare wire of Fig. 5 does, and thusrestricts the adherence of the insulating material to the windingsurface of the coil as previously described. In making coils on thismandrel after the coils are wound, the ends are socured to the mandrelin the usual manner to prevent premature unwinding, and the binding filminsolution is appliedio the exterior of the coil winding. When tried,the b lts 87 and 38 are removed and the mandrel section spacing element39 is removed to permit the clappings of the man drcl inwardly, leavingthe finished coil in self-sustaining form free from the mandrel.

I find that my invention may also be practiced where the turns of wireare tightly wound by a machine having what is known as an automaticscrew machine threading attachment, whereby the mandrel is advancedaxially at a proper speed to provide the proper spacing of successiveconvolutions of coil winding.

It will be understood from the foregoing description that I constructeda coil having spaced convolutions maintained in the desired position byinsulating material which does not extend an undesired distance into thespaces between the convolutions. as a result of which the current lossesdue to capacity between convolutions of the coil are maintained at aminimum.

It will also be understood that various insulating materials other thanthe above mentioned celluloid and in various forms and consistencies maybe used as full equivalents thereof provided, of course, that theypossess the property of adhering to and supporting the convolutions ofthe coil without introducing capacity losses due to marked penetrationbetween the coils.

Having described my invention in certain specific embodiments andemploying generically a novel method of manufacture and a novel methodof application and specific embodiments of such generic invention, I amaware that numerous and extensive departures may be made from theembodiments herein illustrated and described but without departing fromthe spirit of my invention.

I claim:

1. The method of making an inherently form-sustaining coil forelectrical currents, comprising first arranging the successiveconvolutions of the winding in a single layer and spaced apart, thencementing a binding insulating film to one of the winding surfaces, withthe film making only an approximately tangential contact with thedifferent winding convolutions, then in drying the bindin film andrendering the film self sustaining and winding supporting.

2. The method of making an inherently form-sustaining coil for radiofrequency currents comprising first arranging the successiveconvolutions of the winding spaced separately from each other and in asingle layer, then in applying a binding film of syrup-like consistencyto a winding surface of each convolution of the coil with the filmmaking only an approximately tangential cementing contact with theditferent convolutions, then in congealing the binding film to solidform while mechanically holding the winding convolutions in their desired relative spaced )ositions until the binding film is congealed intosolid selfsustaining form.

3. The method of making an inherently form-sustaining coilhaving spacedturns of wire for radio frequency currents, comprising the winding of aconducting wire and a filler wire, side by side, into helical form, thenin applying a binding film of syruplike consistency to one side of thecoil convolutions of the/said wires, making only an approximatelytangential contact with the different winding convolutions, then indrying the binding film in cenientitious relation with the windingconvolutions, while mechanically holding the windim in its desired formuntil the binding film is congealed into solid form, then in removingthe filler wire of the double winding by withdrawin it from that side ofthe coil to which t e binding film is not applied.

4. A coil com rising a helix of conducting wire, the convo utions ofwhich are spaced apart, a sheet of insulating material touching awinding surface of said coil throughout substantially its entire length,the space between the convolutions being open and substantially freefrom insulating material and the convolutions being cemented to the saidsheet.

5. A coil comprising a helix of conducting wire, the convolutions ofwhich are spaced apart, a sheet of insulating material surrounding saidcoil and touching the outer windin surface of said coil throughoutsubstantially its entire length, the space between the convolutionsbeing open and the convolutions being cemented to the sheet.

6. A coil comprising a helix of conducting Wire, the convolutions ofwhich are spaced apart, a sheet of collodion touching a windin surfaceof said coil throughout substantialIy its entire length, the spacebetween the convolutions being open and the convolutions being cementedto the sheet.

7. An inductance coil comprising a helix of conducting wire, a sheet ofinsulating material touching and adhering to a surface of said helixthroughout substantially its entire extent, the wire making contact withthe sheet on only a small segment of its circumference.

8. A coil comprising a space wound helix of conducting wire, helixsupporting insulating material extending lengthwise of the helix forsubstantially the entire axial length thereof and touching and adheringto a surface of said helix, the wire making contact with the insulatingmaterial on only a small segment of the circumference of the wire.

In testimony whereof I hereunto afiix my signature this Qith day ofApril, 1924.

JOHN AUSTIN VICTOREEN.

